Exploring the Formation of Calcium Orthophosphate‐Pyrophosphate Chemical Gardens

Chemical gardens are characterised by the self‐assembly of mineralised abiotic architectures. Utilising the fundamental building blocks of bone mineral, namely calcium and orthophosphate ions, chemical gardens that recapitulate microstructural and compositional features of hard tissue can be grown. Interplay between orthophosphate and pyrophosphate species is highly relevant to natural mineral deposition processes, though this has yet to be explored in the context of generating biologically relevant chemical gardens. Here, tubular calcium orthophosphate‐pyrophosphate chemical gardens were grown from the interface between calcium loaded hydrogels ([Ca2+]=1 M) layered with different orthophosphate‐pyrophosphate solutions ([Pi]+[PPi]=0.7 M). We determine the effect of solution pyrophosphate content on chemical garden morphology and growth rate. Extracted structures were analysed by means of powder X‐ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and X‐ray fluorescence spectroscopy (XRF), revealing orthophosphate‐pyrophosphate solution dependent differences in precipitated mineral crystallinity, composition and microstructure, respectively. Lastly, the potential application of the structures is discussed in the context of tissue engineering and regenerative medicine.